1. Field of the Invention
The present invention relates to a vehicular air conditioner system having a function to recover the waste heat of a heating part such as a driving device and, more particularly, to a vehicular air conditioner system which is improved in the heating capacitance at a low ambient temperature by making a gas injection cycle in a heat pump system capable of at least heating. The present invention is suitable as an air conditioning heat pump system for an electric car for arctic areas and a hybrid car equipped with both an electric motor and an internal combustion engine as its prime mover.
2. Description of Related Art
When a heat pump system using an electric compressor is to be mounted on a vehicle such as an electric car, it is necessary for retaining safety of the vehicle drive to defrost the windshield or to prevent it from becoming misty. In Japanese Patent laid-Open No. 5-319077, therefore, there has been proposed a system which is enabled by providing a cooling-dedicated evaporator and a heating-dedicated evaporator independently of each other as a compartment heat exchanger to prevent the windshield from being clouded with the condensed water due to an abrupt evaporation at the time of changing the mode from the cooling to the heating modes and to dehumidify and heat the conditioned air by heating the air again to a desired temperature with the heating-dedicated condenser while dehumidifying it with the cooling-dedicated evaporator.
According to the aforementioned system of the prior art, however, when the ambient temperature in the circumstances using the system lowers, the heat extraction in an outdoor heat exchanger acting as the evaporator at the heating time is reduced to lower the suction pressure of a compressor so that the capacity to the refrigerant is enlarged to reduce the refrigerant circulation, thus raising a problem that the heating capacity lowers.
When the compressor suction pressure drops, moreover, the compression ratio rises to raise the refrigerant discharge temperature so that the compressor cannot be used with its maximum capacity (or highest RPM) for protecting it. This raises a problem that the heating capacity is further lowered.
From this reasoning, the aforementioned system of the prior art is short of the compartment heating capacity in an arctic area having an ambient temperature of -10.degree. C. or less.
In Japanese Patent Laid-Open No. 54-140247, in order to improve the heating capacity at a low ambient temperature, there has also been proposed an air conditioner which is equipped with a vapor-liquid separator for separating the vapor and liquid of the refrigerant, as regulated to an intermediate pressure, to construct a gas injection type heat pump for injecting the gas refrigerant, as separated by the vapor-liquid separator, into the compression stroke of the compressor and which is further equipped with an auxiliary heat exchanger disposed upstream of the vapor-liquid separator for heating the refrigerant with the air.
In the electric car, however, there is generally adopted a cooling system for cooling a semiconductor switching element or the like of an RPM controlling inverter of a vehicular driving electric motor. In this system, the waste heat of the heating part is extracted to the cooling water, and this cooling water is circulated in a radiator by a water pump so that the waste heat may be released to the atmosphere by the radiator. However, this system has the complicated construction for the heat release through the circulation of the cooling water and requires such a large space for mounting it on the vehicle as to be troubled by retaining the space.
Because the heat pump of the prior art has an ordinary construction, moreover, only one indoor heat exchanger is disposed for both the cooling and heating operations. This heat exchanger cannot exhibit the dehumidifying heating function to heat again the dehumidified conditioned air to a desired temperature. Under a running condition in which the air to be sucked has a high humidity, therefore, there arises a problem that the windshield is liable to become misty.
Since the refrigerant is heated by the auxiliary heat exchanger of an air heat source, on the other hand, the refrigerant heating effect cannot be fully exhibited at the low ambient temperature so that a sufficient heating capacity cannot be expected.